This invention generally relates to techniques for operating movement of a microstructure. More particularly, the present invention provides a method for operating movement of a micro-mirror structure coupled to a pair of torsion bars. Merely by way of example, the present invention is implemented on a micro-mirror device for switching an optical signal, but it would be recognized that the invention has a much broader range of applicability. The mirror can be used in a switching device for long haul communications. The invention can be applied to other types of networks including local area networks, enterprise networks, small switch designs (e.g., two by two) and the like.
According to the present invention, a technique including a method and apparatus for operating a mirror assembly for switching applications. More particularly, the present invention provides a method for operating movement of a micro-mirror structure coupled to a pair of torsion bars. Merely by way of example, the present invention is implemented on a micro-mirror assembly for switching an optical signal, but it would be recognized that the invention has a much broader range of applicability. The mirror can be used in a switching device for long haul communications. The invention can be applied to other types of networks including local area networks, enterprise networks, small switch designs (e.g., two by two) and the like.
As the need for faster communication networks becomes more desirable, digital telephone has progressed. Conventional analog voice telephone signals have been converted into digital signals. These signals can be 24,000 bits/second and greater in some applications. Other telephone circuits interleave these bit streams from 24 digitized phone lines into a single sequence of 1.5 Mbit/second, commonly called the T1 or DS1 rate. The T1 rate feeds into higher rates such as T2 and T3. A T4 may also be used. Single mode optical fibers have also been used at much higher speeds of data transfer. Here, optical switching networks have also been improved. An example of such optical switching standard is called the Synchronous Optical Network (SONET), which is a packet switching standard designed for telecommunications to use transmission capacity more efficiently than the conventional digital telephone hierarchy, which was noted above. SONET organizes data into 810-byte xe2x80x9cframesxe2x80x9d that include data on signal routing and designation as well as the signal itself. The frames can be switched individually without breaking the signal up into its components, but still require conventional switching devices.
Most of the conventional switching devices require the need to convert optical signals from a first source into electric signals for switching such optical signals over a communication network. Once the electric signals have been switched, they are converted back into optical signals for transmission over the network. As merely an example, a product called the SN 16000 is BroadLeaf(trademark) Network Operating System (NOS) made by Sycamore Networks, Inc. uses such electrical switching technique. Numerous limitations exist with such conventional electrical switching technique. For example, such electrical switching often requires a lot of complex electronic devices, which make the device difficult to scale. Additionally, such electronic devices become prone to failure, thereby influencing a reliability of the network. The switch is also slow and is only as fast as the electrical devices. Accordingly, techniques for switching optical signals using a purely optical technology have been proposed. Such technology can use a wave guide approach for switching optical signals. Unfortunately, such technology has been difficult to scale for switching a high number of signals from a bundle of optical fibers, which may be desirable today. Other companies have also been attempting to develop technologies for switching such high number of signals, but have been unsuccessful. Such switches are also difficult to manufacture effectively and reliably. Other examples of optical switching networks include access, metropolitan and Dense Wavelength Division Multiplexing (DWDM) networks.
As merely an example, some companies have been attempting to use mirrors to switch an optical beam from one fiber to another. The use of mirrors in telecommunication signals has some advantages such as low signal loss and the like. Such mirrors, however, are often difficult to manufacture in a high density mirror array. In particular, such mirrors are often fragile and prone to damage during fabrication. U.S. Pat. No. 5,969,465, assigned to XROS, Inc. describes such a mirror, which is often difficult to make and operate high density array structures. Such mirrors can often only operate in a stable region through electrostatic force. Such stable region generally provides a limited amount of movement of the mirror through a spatial region, which limits its switching effectiveness. Accordingly, it is often difficult to use such a mirror design to operate high density arrays.
From the above, it is seen that an improved way for operating movement of a mirror assembly for switching a signal is highly desirable.
According to the present invention, a technique including a method and apparatus for operating a mirror assembly for switching applications. More particularly, the present invention provides a method for operating movement of a micro-mirror structure coupled to a pair of torsion bars. In an exemplary embodiment, the invention provides a method for operating an unstable micro-opto-electro mechanical systems (i.e., MOEMS). Merely by way of example, the present invention is implemented on a micro-mirror device for switching an optical signal, but it would be recognized that the invention has a much broader range of applicability. The mirror can be used in a switching device for long haul communications. The invention can be applied to other types of networks including local area networks, enterprise networks, small switch designs (e.g., two by two) and the like.
In a specific embodiment, the invention provides a method of switching optical signals using micro-mirror structures and control. The method selects an optical path for a micro-mirror device, the mirror device being coupled to a torsion bar device. The micro-mirror device is moved or pivoted about a torsion bar device, the micro-mirror device being operated about the torsion bar device through an operating range including a stable region and an unstable region. The micro-mirror device is subjected to a mechanical force from the torsion bar and being subjected an electro-static force applied to the micro-mirror device. The method positions the micro-mirror device to a selected switching location within the operating range through the stable region and to a selected region within the unstable region within a predetermined time. The micro-mirror device is controlled during a portion of time during its movement by receiving position signals periodically at a predetermined frequency from a sensing device coupled to the micro-mirror device. The position signals are indicative of a position of the operating range and selectively applying an electrostatic force based upon one or more of the position signals such that the micro-mirror device is moved to the selected switching location without substantial oscillation of the micro-mirror device within the predetermined time of less than 10 milliseconds.
Many benefits are achieved by way of the present invention over conventional techniques. For example, the present technique provides an easy to use process that relies upon conventional technology. The present invention provides a novel way of controlling and operating a MOEMS, which can include a micro-mirror assembly. In one aspect, the invention allows for high scale integration of mirror devices to form high density and performance switching devices. Such switching device can include more than 10 (ten) mirror elements. In some embodiments, such switching devices can include more than 200 (two hundred) or even thousands (one thousand to four thousand and greater) mirror elements for switching respective signals for optical switching applications. The invention also provides for a stable switch position during operation for a MOEMS, which may be subjected to internal and/or external noise from a mechanical (e.g., vibration, shock), thermal, gravitational or electrical force or forces. Such forces can be detrimental to precise switching requirements of the MOEMS for optical switching applications in optical networking applications. The present feed back control can also provide for stable operation that may be related to drift caused by electrical, mechanical, and/or thermal. The invention can also take into account degradations over a lifetime of a switching device, which may be prone to fatigue or the like. In preferred embodiments, the present system has stable operating performance (e.g., low bit error rates, low dB losses, low insertion losses) due to the feed back process. The present control system can be used to reduce switching time (e.g., less than 20 milliseconds) as compared to conventional open loop configurations, which often oscillate and cannot find a stable position efficiently. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more throughout the present specification and more particularly below.
Various additional objects, features and advantages of the present invention can be more fully appreciated with reference to the detailed description and accompanying drawings that follow.